| disease | Diving-related Inner Ear Injury |
| alias | Decompression Sickness |
This disease is also known as decompression sickness (Decompression sickness). In 1973, Smith first described this condition as caisson disease (Caisson disease), which refers to inner ear injury caused by rapid pressure changes in the high-pressure environment of diving. The incidence rate among divers during operations is 1%. Generally, for every 10 meters descended underwater, the water pressure increases by one atmosphere, equivalent to applying 17–18 Mg of pressure on the human body. Therefore, divers must inhale compressed air or a mixture of inert gas and oxygen to regulate the internal and external pressure of the tympanic cavity and nasal cavity. If the pressure changes too quickly or if the eustachian tube malfunctions, the disease can occur.
bubble_chart Pathological Changes
(1) Temporary Vestibular Dysfunction
1. Stimulation by water of different temperatures entering the external or middle ear. Due to obstruction of the external auditory canal or perforation of the tympanic membrane, water entering the external or middle ear creates a temporal and temperature difference, leading to vestibular stimulation effects.
2. Dysfunction of the eustachian tube prevents automatic regulation of middle ear pressure. After diving, ascending to the surface creates a relative high-pressure state, leading to implosive injuries such as dislocation of the auditory ossicles, rupture of the window membrane, or simple stapes displacement, which can cause vertigo. In severe cases, vortices in the perilymph of the inner ear may injure the basal turn of the cochlea, resulting in permanent deafness. Both ascent and descent during diving can cause barometric vertigo. According to Lundgren (1974), the incidence rate is 17%. Symptoms disappear upon returning to the original water depth, with no permanent damage.
3. High-pressure nervous syndrome. First termed by Brauer in 1968, this occurs when diving deeper than 150m while breathing a helium-oxygen mixture. Due to the rapid increase in pressure, symptoms such as dizziness, tremor, and psychomotor disturbances may occur, but they quickly resolve after decompression. According to Farmer (1971), this condition is not caused by tissue hypoxia or carbon dioxide accumulation in the blood but by weakened cerebellar inhibition of vestibular nucleus function.(2) Permanent Inner Ear Damage
1. Decompression sickness during ascent or descent in shallow diving, or poor eustachian tube function during deep diving under pressure, combined with incorrect eustachian tube inflation, can cause a sharp rise in cerebrospinal and perilymphatic fluid pressure. This may lead to inward displacement of the stapes into the tympanic cavity, rupture of the vestibular membrane, and perforation of the tympanic membrane. According to Harker's (1974) experiments, a pressure difference of 16 kPa (equivalent to 1.58m of seawater depth) across the tympanic membrane can cause implosive membrane rupture.
2. Sudden unilateral vestibular failure can occur during stable deep diving. First reported by Sundmaker in 1973, symptoms may arise shortly after switching from breathing a helium-oxygen or helium-neon-oxygen mixture to air during deep diving. This may be due to the added gases increasing the gas concentration in the endolymph, causing osmotic edema, or the interaction of newly introduced inert gases with previously absorbed nitrogen, forming bubbles upon decompression and leading to inner ear gas embolism.
3. Noise levels of 100–120 dB generated by ventilation or compressed gas in caissons or diving helmets can cause noise-induced inner ear damage.
During decompression, divers can develop vertigo, nausea, vomiting, tinnitus, and deafness within half an hour. Objective examinations may reveal spontaneous nystagmus. Caruso (1977) reported 11 cases of decompression sickness, where peripheral injuries included tinnitus, deafness, and prolonged vertigo. One case involved a fracture of the stapes footplate and perilymphatic fistula, along with diffuse central nervous system damage symptoms such as poor memory, blurred vision, abnormal somatic sensations, joint pain, and limb weakness.
bubble_chart Treatment Measures
1. After symptoms appear, immediate recompression or returning to the original water pressure should be performed. Wait until the symptoms disappear before slowly decompressing. According to Farmer's opinion, the depth of recompression should generally be three atmospheres (30.48m) below the depth where symptoms appeared. If mixed gas was previously inhaled, it should be resumed at this time, and decompression should only proceed after the condition improves.
2. For dizziness and tinnitus, elevate the head and administer pressurized oxygen inhalation. Diazepam may also be used to alleviate symptoms.
3. The use of heparin offers more disadvantages than benefits and is no longer employed.
4. Individuals with tympanic membrane perforation or dysfunctional eustachian tubes should avoid diving operations.
